72 PROCEEDIXGS OF THE SAIXT LOUIS MEETING 



evidence, it remains to consider whether the subsidence has been due to the 

 depression of broad areas of the ocean floor or to relatively local subsidence 

 of the reef foundations, which in most cases are volcanic islands. A broad 

 subsidence of the ocean floor would lower the ocean surface and presumably 

 cause the emergence of marine strata around the greater part of the conti- 

 nental margins. The local subsidence of many volcanic islands, on which reefs 

 are built up as the islands subside, would leave the ocean surface somewhat 

 higher than it was before the islands were formed, and this would tend to 

 raise the ocean on the continental margins and to embay their shorelines. As 

 continental shorelines are very generally embayed, this evidence, as far as it 

 goes, indicates that the subsidence which gave opportunity for reef upgrowth 

 was relatively local. Confirmation is thus found for the suggestion recently 

 made by Molengraaf that the subsidence of volcanic islands is an isostatic 

 phenomenon. 



Presented by title in the absence of the author. 



STRUCTURE OF SOME MOUNTAINS IN NEW MEXICO 

 BY N. H. DARTOX 



(Abstract) 



In a detailed investigation of the red beds of New Mexico the author has 

 had opportunity to observe the structure of various mountain ranges, espe- 

 cially in the central, eastern, and southern parts of the State. A great variety 

 of interesting details are presented, but faulted tilted blocks are the most 

 numerous. Physiographic features are in part dependent on structure and in 

 part independent of it, excepting so far as to influence the altitude and dis- 

 tribution of hard and soft rocks. 



Read by title in the absence of the author. 



IMPORTANCE OF NIVATION AS AN EROSIVE FACTOR AND OF SOIL FLOW AS 

 A TRANSPORTING AGENCY IN NORTHERN GREENLAND 



BY W. ELMER EKBLAW ^ 



(Abstract) 



Nivation is one of the most important erosive factors in northern Greenland. 

 Especially is this true where the wind piles the snow in drifts. 



Dome-shaped drifts of snow form on plateaus, plains, and most compara- 

 tively level surfaces : "piedmont" drifts form along cliffs ; "wedge" drifts form 

 in gullies and small gorges near the top of cliffs. Each of these drifts pro- 

 duces different results. The dome-shaped drifts result in horizontal solifluc- 

 tion and altiplanation terraces ; the piedmont drifts result in solifluction slopes, 

 and "wedge" drifts initiate cirques. These "wedge" drifts may develop into 

 glaciers, or they may develop into circular "piedmont" drifts, as the gorge 

 gradually changes into a cirque. In this latter case the snow completes the 

 formation of the cirque. 



1 Introduced hy W. fi. Bay ley. 



